: This proposal is to continue the follow-up of children and young adults who were treated successfully for Wilms tumor on protocol studies of the National Wilms Tumor Study Group (NWTSG). Patients will be contacted annually and those who become lost will be actively traced. Information on health status and key events will be obtained from periodic physical exams and medical histories, with medical records used to confirm reproductive outcomes and key diagnoses. The goals are to help elucidate the genetic events involved in the pathogenesis of Wilms tumor, to estimate the risk of adverse pregnancy outcomes and congenital defects in offspring, and to determine the risks of second malignant neoplasms, congestive heart failure and renal failure in survivors.Adjuvant treatment for Wilms tumor involves the combination of several chemotherapeutic agents with or without radiation therapy. This facilitates comparison of rates of key events among randomized subgroups of patients that differ with respect to the dose and duration of use of radiation and specific drugs. Data on the occurrence of Wilms tumor in family members and offspring will facilitate testing of specific genetic models and the estimation of recurrence risks for use by clinical geneticists in counselling affected families. Although initially believed to exemplify Knudson's two stage mutational model in a manner similar to retinoblastoma, the genetics of Wilms tumor is now recognized to be more complex and heterogeneous. The proposed epidemiologic studies will provide insights regarding carcinogenic mechanisms that can be used to orient and interpret the laboratory studies. Collaboration with groups of molecular biologists, providing them national access to informative subgroups of patients, will speed their discoveries.